1. Field of the Invention
This invention relates to an improvement in composite outsoles of the type having a bottom element forming the tread surface and an upper element molded to the top surface of the bottom element.
2. Description of the Prior Art
A bottom view of a prior art outsole 10 is shown in FIG. 1, and a cross section of the same outsole is shown in FIG. 2 at the conclusion of the molding operation. The outsole 10 includes a substantially planar first element 12 of rubber-like material having a bottom tread surface which is typically scored or grooved as at 14. The first element 12 is appropriately configured and dimensioned to be received in a central cavity 16 in the base 18 of a two part mold. The cavity 16 is surrounded by an upstanding rim 20, which in turn is surrounded by a relatively wide channel 22. In order to ensure that the first element 12 lies flat within the cavity 16, it is necessary to provide some small clearance 24 between its peripheral side edge and the surrounding rim 20. The mold is closed by a lid 26, and a second element 28 of the outsole is molded onto the top surface of the first element 12. Typically, the second element is formed from a foamable material, e.g., polyurethane, which is introduced into the mold in a liquid state and allowed to foam in place.
A problem with this arrangement is that during the foaming step, the internal mold pressure sometimes forces some of the liquid foamable material through the clearance 24 and into the scores, grooves or spaces 14 in the bottom tread surface of the first element. When this occurs, as indicated for example at 30 in FIGS. 1 and 2, the resulting product is defective and must be scrapped.
The objective of the present invention is to avoid the above-described problem by effectively blocking any penetration of the liquid foamable material between the first element and the surrounding mold surfaces.